The present invention relates to a semiconductor device and a semiconductor module and, more particularly, a structure that is able to radiate excellently the heat from the semiconductor element.
In recent years, application of the semiconductor device to the mobile device and the small and high density packaging device makes progress, and thus not only the reduction in size and weight but also the good radiating characteristic is requested. Also, the semiconductor device is mounted onto various substrates, and the semiconductor module containing the substrate is mounted in various devices. As the substrate, there are the ceramic substrate, the printed circuit board, the flexible sheet, the metal substrate, the glass substrate, etc. Here, as the semiconductor module mounted onto the flexible sheet, an example will be explained hereunder. In this case, it is needless to say that these substrates can be employed in embodiments.
A hard disk 100 into which the semiconductor module employing the flexible sheet is mounted is shown in FIG. 25. For example, this hard disk 100 is described in detail in Nikkei Electronics, 1997, Jun. 16 (No.691), p92-.
This hard disk 100 is packaged into a casing 101 formed of metal, and plural sheet of recording disks 102 are fitted integrally to a spindle motor 103. A magnetic head 104 is arranged over a surface of the recording disk 102 via a minute clearance respectively. This magnetic head 104 is fitted to a top end of a suspension 106 that is fixed to the top of an arm 105. Then, an integral structure consisting of the magnetic heads 104, the suspension 106, and the arm 105 is fitted to an actuator 107.
The recording disks 102 must be connected electrically to a read/write amplifier IC 108 to execute the writing/reading via the magnetic heads 104. Thus, a semiconductor module 110 in which the read/write amplifier IC 108 is mounted onto a flexible sheet 109 is employed. Wirings provided on the flexible sheet 109 are finally connected electrically the magnetic heads 104. The semiconductor module 110 is called the flexible circuit assembly and is normally abbreviated to FCA.
A connector 111 fitted onto the semiconductor module 110 is exposed from a back surface of the casing 101. This connector (male or female type) 111 is connected to another connector (female or male type) fitted to a main board 112. Also, wirings are provided on the main board 112, and also a driving IC for the spindle motor 103, a buffer memory, other driving ICs, e.g., ASIC, etc. are mounted.
For example, the recording disk 102 is rotated by the spindle motor 103 at 4500 rpm, and a position of the magnetic head 104 is decided by the actuator 107. Since this rotating mechanism is tightly sealed by a lid provided to the casing 101, the heat is filled inevitably in the casing 101 and thus the temperature of the read/write amplifier IC 108 is increased. Therefore, the read/write amplifier IC 108 is positioned on the actuator 107, the casing 101, or the like, that has excellent thermal conduction. Also, the rotation of the spindle motor 103 tends to increase such as 5400, 7200, 10000 rpm, and thus this heat radiation becomes important more and more.
In order to explain the above semiconductor module (FCA) 110 further more, a structure of the semiconductor module is shown in FIG. 26. FIG. 26A is a plan view and FIG. 26B is a sectional view in which the read/write amplifier IC 108 provided to the top portion is cut out along an A-A line. Since this FCA 110 is folded and then fitted into a part of the casing 101, a first flexible sheet 109 having a flat shape that can be easily folded is employed.
The connector 111 is fitted to the left end of the FCA 110 to act as a first connector portion. First wirings 121 electrically connected to the connector 111 are stuck to the first flexible sheet 109 and then extended to the right end. Then, the first wirings 121 are electrically connected to the read/write amplifier IC 108. Also, leads 122 of the read/write amplifier IC 108 connected to the magnetic heads 104 are connected to second wirings 123. The second wirings 123 are electrically connected to third wirings 126 on the second flexible sheet 124 provided over the arm 105 and the suspension 106. That is, the right end of the first flexible sheet 109 constitutes a second connecting portion 127, and is connected to the second flexible sheet 124 there. The first flexible sheet 109 and the second flexible sheet 124 may be integrally formed. In this case, the second wirings 123 and the third wirings 126 are integrally provided.
A supporting member 128 is provided on a back surface of the first flexible sheet 109 on which the read/write amplifier IC 108 is provided. The ceramic substrate or the Al substrate is employed as this supporting member 128. The heat generated by the read/write amplifier IC 108 can be discharged since the metals exposed in the casing 101 is thermally coupled with the outside via the supporting member 128.
Then, a connection structure of the read/write amplifier IC 108 and the first flexible sheet 109 will be explained with reference to FIG. 26B hereunder.
This first flexible sheet 109 is formed by laminating a first polyimide sheet 130 (referred to as a xe2x80x9cfirst PI sheetxe2x80x9d hereinafter), a first adhering layer 131, a conductive pattern 132, a second adhering layer 133, and a second polyimide sheet 134 (referred to as a xe2x80x9csecond PI sheetxe2x80x9d hereinafter) from the bottom. The conductive pattern 132 is sandwiched between the first PI sheet 130 and the second PI sheet 134.
Also, in order to connect the read/write amplifier IC 108, an opening portion 135 is formed by removing the second PI sheet 134 and the second adhering layer 133 from a desired area to expose the conductive pattern 132. Then, as shown in FIG. 26B, the read/write amplifier IC 108 is electrically connected via the leads 122.
In FIG. 26B, the heat is radiated from the semiconductor device being packaged with an insulating resin 136 to the outside via the heat radiation path indicated by arrows. More particularly, the semiconductor device in the prior art has such a structure that, since an insulating resin 136 acts as a thermal resistance, the heat generated from the read/write amplifier IC 108 cannot be effectively discharged to the outside in total.
Then, the hard disk will be explained hereunder. The transfer rate of the hard disk in reading/writing needs the frequency of 500 MHz to 1 GHz, or more so as to increase the reading/writing speed of the read/write amplifier IC 108. Therefore, the wiring path on the flexible sheet connected to the read/write amplifier IC 108 must be reduced and also the increase in the temperature of the read/write amplifier IC 108 must be prevented.
In particular, since the recording disks 102 are rotated at a high speed and are installed in a space of the casing 101 tightly sealed by the lid, the temperature in the casing 101 is increased up to about 70 to 80xc2x0 C. In contrast, the allowable operating temperature of the normal IC is about 125xc2x0 C., and the temperature increase of about 45xc2x0 C. from the internal temperature of 80xc2x0 C. can be accepted for the read/write amplifier IC 108. However, as shown in FIG. 26B, if the thermal resistance of the semiconductor device per se or the thermal resistance of the FCA is large, the read/write amplifier IC 108 exceeds immediately the allowable operating temperature and cannot exhibit its essential ability. As a result, the semiconductor device or FCA having the excellent radiation characteristic is requested.
In addition, there is such a problem that, since the operating frequency is further increased in the future, the temperature increase of the read/write amplifier IC 108 itself is brought about by the heat generated by the operating process. Although the target operating frequency can be achieved in the normal temperature, the operating frequency must be lowered because of its temperature increase in the inside of the hard disk.
As described above, with the increase of the operating frequency in the future, the better radiation characteristic is required for the semiconductor device or the semiconductor module (FCA).
In contrast, the actuator 107 itself, or the arm 105 fitted to the actuator 107, the suspension 106, and the magnetic head 104 must be reduced in weight to reduce their moment of inertia. Especially, as shown in FIG. 25, in case the read/write amplifier IC 108 is mounted on the surface of the actuator 107 or the arm 105, the reduction in weight of the IC 108 and the FCA 110 is also requested.
Moreover, as shown in FIG. 27, there is a semiconductor device in which the island 137 of the read/write amplifier IC 108 is exposed from the insulating resin 136 and the back surface of the island 137 and the contact surface of the lead 122 are formed at the same surface level. In this case, there is the problem, since the connecting means such as the solder, etc., that is formed between the lead 122 and the conductive pattern 132, is formed very thin and thus the clearance between the island 137 and the second PI sheet 134 is very narrow, it is difficult to clean this clearance.
The present invention has been made in view of the above subjects, and can overcome these subjects by satisfying following respects. First, there is provided a semiconductor module comprising: a semiconductor device in which semiconductor elements are sealed integrally by an insulating resin and back surface electrodes that are electrically connected to the semiconductor elements are exposed from a back surface; and a flexible sheet having at least a plurality of conductive patterns, a first insulating sheet for supporting pad electrodes formed at end potions of said conductive patterns and electrically connected to said back surface electrodes, and a second insulating sheet for covering the conductive patterns; wherein an opening portion from which the pad electrodes are exposed and whose size is larger than a back surface of the semiconductor device is formed in the second insulating sheet, and contact areas which come into contact with at least three areas of a back surface of the insulating resin are provided to the opening portion.
If the thickness of contact areas is set to about 40 to 50 xcexcm or more, the clearance can be formed between the back surface of the semiconductor device and the first insulating sheet and can be cleaned.
Second, the contact areas are formed of the second insulating sheet. As shown in FIG. 1 and FIG. 4, the second insulating sheet is employed as the spacers, the clearance can be formed on the back surface of the semiconductor device.
Third, the contact areas are formed integrally with the second insulating sheet.
Fourth, the contact areas are formed of material which is different from the second insulating sheet.
Fifth, there is provided a semiconductor module comprising: a semiconductor device in which semiconductor elements are sealed integrally by an insulating resin, back surface electrodes that are electrically connected to the semiconductor elements are exposed from a back surface at a same surface level as a back surface of the insulating resin or a hollow surface level rather than the back surface, and an island provided to a lower surface of the semiconductor element is exposed at the same surface level as the back surface of the insulating resin or the hollow surface level rather than the back surface; and a flexible sheet having at least a plurality of conductive patterns, a first insulating sheet for supporting pad electrodes formed at end potions of said conductive patterns and electrically connected to said back surface electrodes, and a second insulating sheet for covering the conductive patterns; wherein a first opening portion from which the pad electrodes are exposed and whose size is larger than a back surface of the semiconductor device is formed in the second insulating sheet, and a second opening portion which exposes the island from a back surface of the first insulating sheet is formed in the first insulating sheet, and contact areas which come into contact with at least three areas of the back surface of the insulating resin are provided between the first opening portion and the second opening portion.
Since the island of the semiconductor device is exposed from the back surface of the flexible sheet, it can be directly adhered to the material having good thermal conductivity. In addition, the clearance can be formed on the back surface of the semiconductor device because the contact areas act as the spacers, this clearance can be cleaned.
Sixth, the contact areas are formed of the second insulating sheet.
Seventh, the contact areas are formed integrally with the second insulating sheet.
Eighth, the contact areas are formed of material which is different from the second insulating sheet.
Ninth, a radiation substrate is stuck onto a back surface of the first insulating sheet to close the second opening portion, and the radiation substrate and the island are thermally coupled with each other.
Since the island and the semiconductor device are thermally coupled with each other by the solder, etc., the heat generated from the semiconductor device can be transferred to the radiation substrate.
Tenth, a first metal film which contains Cu, Ag or Au as major material and is formed by plating is formed as an uppermost layer on a first surface of the radiation substrate, and the first metal film and the island are adhered to (or are brought into contact with) each other by brazing solder, conductive paste, or adhesive material which is excellent in thermal conductivity.
If Al is employed as the radiation substrate, the radiation substrate and the island can be adhered to each other via the brazing solder by forming the Cu, Ag or Au plated film on the outermost surface.
Eleventh, the first surface of the radiation substrate and the island are adhered to (or are brought into contact with) each other by brazing solder, conductive paste, or adhesive material which is excellent in thermal conductivity.
Twelfth, a radiation substrate is stuck onto a back surface of the first insulating sheet to close the second opening portion, and a metal plate containing Cu as a major component is adhered between the radiation substrate and the island.
When the back surface electrodes and the pad electrodes are connected to each other, the clearance is formed between the island and the radiation substrate by the thickness of the conductive pattern and the thickness of the first insulating sheet. In this case, the metal plate having the thickness almost equal to this clearance can be inserted, the island and the radiation substrate can be excellently thermally coupled with each other.
Thirteenth, the island and the metal plate are substantially formed of same material.
If the projection is formed on the island, the island can be thermally coupled with the radiation substrate without employment of another metal plate.
Fourteenth, the radiation substrate and the metal plate are formed integrally of same material.
If the projection is formed by applying the press, etc. to the radiation substrate, the island can be thermally coupled with the radiation substrate without employment of another metal plate.
Fifteenth, there is provided a semiconductor module comprising: a semiconductor device in which semiconductor elements are sealed integrally in a face-up or face-down fashion by an insulating resin, back surface electrodes that are electrically connected to bonding electrodes of the semiconductor elements are exposed from a back surface at a same surface level as a back surface of the insulating resin or a hollow surface level rather than the back surface, and an island provided to a lower surface of the semiconductor element is exposed at the same surface level as the back surface of the insulating resin or the hollow surface level rather than the back surface; and a flexible sheet having at least a plurality of conductive patterns, a first insulating sheet for supporting pad electrodes formed at end potions of said conductive patterns and electrically connected to said back surface electrodes, and a second insulating sheet for covering the conductive patterns; wherein a first opening portion from which the pad electrodes are exposed and whose size is larger than a back surface of the semiconductor device is formed in the second insulating sheet, and a second opening portion from which a radiation substrate being stuck onto an area corresponding to the island is exposed is provided to a back surface of the first insulating sheet, and contact areas which come into contact with at least three areas of the back surface of the insulating resin are provided between the first opening portion and the second opening portion, and the contact areas come into contact with the back surface of the insulating resin, and the island and the radiation substrate are thermally coupled with each other.
Sixteenth, side surfaces of the back surface electrodes and the back surface of the insulating resin extended from the side surfaces of the back surface electrodes have a same curved surface.
Seventeenth, the semiconductor element is a read/write amplifier IC of a hard disk.
Eighteenth, there is provided a method of manufacturing a semiconductor module, comprising the steps of: preparing a semiconductor device in which semiconductor elements are sealed integrally by an insulating resin and back surface electrodes that are electrically connected to the semiconductor elements and an island provided below the semiconductor elements are exposed from a back surface, and a flexible sheet having at least a plurality of conductive patterns, a first insulating sheet for supporting pad electrodes formed at end potions of said conductive patterns and electrically connected to said back surface electrodes, and island-like electrodes adhered to said island, and a second insulating sheet for covering the conductive patterns, wherein an opening portion from which the pad electrodes and the island-like electrode are exposed and whose size is larger than a back surface of the semiconductor device is formed in the second insulating sheet; connecting electrically the pad electrodes and the back surface electrodes and mounting the semiconductor device via spacers provided under the semiconductor device; and cleaning a clearance formed by the spacers via the opening portion exposed from peripheries of the semiconductor device.
Since the cleaning liquid can be permeated into the clearance, the degradation or the failure of the electrical connecting portions arranged in the clearance can be prevented.
Nineteenth, there is provided a method of manufacturing a semiconductor module, comprising the steps of: preparing a semiconductor device in which semiconductor elements are sealed integrally by an insulating resin and back surface electrodes that are electrically connected to the semiconductor elements are exposed from a back surface, and a flexible sheet having at least a plurality of conductive patterns, a first insulating sheet for supporting pad electrodes formed at end potions of said conductive patterns and electrically connected to said back surface electrodes, and a second insulating sheet for covering the conductive patterns, wherein an opening portion from which the pad electrodes are exposed and whose size is larger than a back surface of the semiconductor device is formed in the second insulating sheet; connecting electrically the pad electrodes and the back surface electrodes and mounting the semiconductor device while providing a clearance on a back surface via contact areas provided integrally with the first insulating sheet; and cleaning the clearance formed on the back surface of the semiconductor device via the opening portion exposed from peripheries of the semiconductor device.
Twentieth, there is provided a method of manufacturing a semiconductor module, comprising the steps of: preparing a semiconductor device in which semiconductor elements are sealed integrally by an insulating resin and an island provided below the semiconductor elements and back surface electrodes that are electrically connected to the semiconductor elements are exposed from a back surface, and a flexible sheet having at least a plurality of conductive patterns, a first insulating sheet for supporting pad electrodes formed at end potions of said conductive patterns and electrically connected to said back surface electrodes and from which a radiation substrate stuck onto a back surface is exposed, and a second insulating sheet for covering the conductive patterns, wherein an opening portion from which the pad electrodes and the radiation substrate are exposed and whose size is larger than a back surface of the semiconductor device is formed in the second insulating sheet; connecting electrically the pad electrodes and the back surface electrodes, coupling thermally the island with the radiation substrate, and mounting the semiconductor device while providing a clearance on a back surface via contact areas provided at at least three areas of the back surface of the insulating resin; and cleaning the back surface of the semiconductor device via the opening portion exposed from peripheries of the semiconductor device.
Twenty-first, underfill is mixed into the back surface of the semiconductor device after the cleaning.